95 D1 hot start issue (when off roading)

[El Pinchi]

My D1 has had this problems for about 6 yrs and no mechanic friends can figure this out! I have a 4.6, Mallory ignition, rotor and module new, Bosch coil good, have spark, fuel pressure, new fuel pump.
Problem: when I’m off roading driving slowly like 10-15 mph for hrs, engine will not start if I turn off engine. I have to open the hood, let it cool off for 30 mins-1 hr and it might start. I also noticed that the coil gets really hot but I’m not sure if that’s normal. It cranks and turns over but won’t start. Also, if I drive on the freeway for any long period of time like an hr, the same thing happens if I turn off engine. So, something heat related is my guess but I just can’t figure it out. Any advice in what I should check is appreciated. Thanks! Ed

 

[pmatusov]

Eddie,
when that happens, do you still have spark? you can unhook the high-voltage wire from the center of the distributor cap, and put it near the body or engine, so that the terminal is separated from the ground by ~3/8". Have somebody to turn the key and observe the presence (or absence) of the spark.
If you don't have the spark, slowly pour a bottle of water on the coil. If the engine starts after that, coil is your culprit. Same thing, generally, applies to the ignition module, but I am not familiar with Mallory modules.

 

[El Pinchi]

Peter, yes I do have spark.

 

[rocky]

I had a similar scenario. Two potential causes:
1: The coil, while good when cold, has insufficient coolant in it. As a result, it overheats during use. Coils can and do leak.
2: I’ve had bad Bosch coils in the past.
Change the coil with a known good one.

 

[El Pinchi]

I had a similar scenario. Two potential causes:
1: The coil, while good when cold, has insufficient coolant in it. As a result, it overheats during use. Coils can and do leak.
2: I’ve had bad Bosch coils in the past.
Change the coil with a known good one.

I’ve tried changing the coil once before and it still happened. I just ordered another new one and I’ll try that again.

 

[pmatusov]

Well, if you have spark on a hot engine and no-start condition, that's not the coil or amp.
I'd check the fuel pressure on the rail and the resistance of the coolant temp sensor.

 

[jymmiejamz]

Try unplugging the coolant temp sensor. It will default to 95F from what I remember and it will result in a slightly extended crank

 

[Z.G]

Try unplugging the coolant temp sensor. It will default to 95F from what I remember and it will result in a slightly extended crank

Coolant temp sensor or fuel temp sensor, the fuel temp sensor causes this same issue too

 

[rocky]

I’ve tried changing the coil once before and it still happened. I just ordered another new one and I’ll try that again.

When the Bosch premature failure issue happened, it was a batch of them bought from same source. Buying from a different source solved the issue.

 

[JDFRRC]

Solved?

 

[El Pinchi]

Solved?

When the Bosch premature failure issue happened, it was a batch of them bought from same source. Buying from a different source solved the issue.

Rocky, I think your suggestion was dead on. I changed the coil again with a new one and I had no starting issues on my last trip. Need to test it out more on a few more hotter, longer trips but so far, it looks promising!

I think so but I’ve only taken it on one trip off road.

 

[rocky]

That’s ok. Have your next replacement handy in your traveling parts bin….. sure fire way to ensure no more problems….